diff --git a/src/s1ap/asn1c/asnGenFiles/constr_CHOICE.h b/src/s1ap/asn1c/asnGenFiles/constr_CHOICE.h
new file mode 100644
index 0000000..a1999ed
--- /dev/null
+++ b/src/s1ap/asn1c/asnGenFiles/constr_CHOICE.h
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2003-2017 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#ifndef	_CONSTR_CHOICE_H_
+#define	_CONSTR_CHOICE_H_
+
+#include <asn_application.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct asn_CHOICE_specifics_s {
+	/*
+	 * Target structure description.
+	 */
+	unsigned struct_size;       /* Size of the target structure. */
+	unsigned ctx_offset;        /* Offset of the asn_codec_ctx_t member */
+	unsigned pres_offset;       /* Identifier of the present member */
+	unsigned pres_size;         /* Size of the identifier (enum) */
+
+	/*
+	 * Tags to members mapping table.
+	 */
+	const asn_TYPE_tag2member_t *tag2el;
+	unsigned tag2el_count;
+
+	/* Canonical ordering of CHOICE elements, for PER */
+	const unsigned *to_canonical_order;
+	const unsigned *from_canonical_order;
+
+	/*
+	 * Extensions-related stuff.
+	 */
+	signed ext_start; /* First member of extensions, or -1 */
+} asn_CHOICE_specifics_t;
+
+/*
+ * A set specialized functions dealing with the CHOICE type.
+ */
+asn_struct_free_f CHOICE_free;
+asn_struct_print_f CHOICE_print;
+asn_struct_compare_f CHOICE_compare;
+asn_constr_check_f CHOICE_constraint;
+ber_type_decoder_f CHOICE_decode_ber;
+der_type_encoder_f CHOICE_encode_der;
+xer_type_decoder_f CHOICE_decode_xer;
+xer_type_encoder_f CHOICE_encode_xer;
+oer_type_decoder_f CHOICE_decode_oer;
+oer_type_encoder_f CHOICE_encode_oer;
+per_type_decoder_f CHOICE_decode_uper;
+per_type_encoder_f CHOICE_encode_uper;
+per_type_decoder_f CHOICE_decode_aper;
+per_type_encoder_f CHOICE_encode_aper;
+asn_outmost_tag_f CHOICE_outmost_tag;
+asn_random_fill_f CHOICE_random_fill;
+extern asn_TYPE_operation_t asn_OP_CHOICE;
+
+/*
+ * Return the 1-based choice variant presence index.
+ * Returns 0 in case of error.
+ */
+unsigned CHOICE_variant_get_presence(const asn_TYPE_descriptor_t *td,
+                                     const void *structure_ptr);
+
+/*
+ * Sets or resets the 1-based choice variant presence index.
+ * In case a previous index is not zero, the currently selected structure
+ * member is freed and zeroed-out first.
+ * Returns 0 on success and -1 on error.
+ */
+int CHOICE_variant_set_presence(const asn_TYPE_descriptor_t *td,
+                                void *structure_ptr, unsigned present);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif	/* _CONSTR_CHOICE_H_ */